Update vcpkg OpenCL port to point here

The [vcpkg OpenCL port](https://github.com/microsoft/vcpkg/blob/master/ports/opencl/portfile.cmake) currently points to old commits of the OpenCL headers and the ICD loader. It should be updated to point to here. That will:
* Update it to current best practices for how to target OpenCL
* Pick up OpenCL 3.0 support in both the ICD loader and the headers

Start with the linked vcpkg OpenCL portfile and compare its referenced OpenCL headers and ICD loader commits with this repository. Update the port to point here and verify that it targets current best practices and picks up OpenCL 3.0 support in both dependencies.

Written by the indexing model from the issue text.